In this work, it was used a polypyrrole (PPy) electrode as a potentiometric electrochemical detector in a flow injection system in order to determine sulfamethoxazole in pharmaceutical formulations. The PPy electrode was prepared by cyclic voltammetry in acetonitrile solution. A linear relationship was observed over the concentration range of 2.5 x 10(-5)-1.25 x 10(-3) mol L(-1) with a correlation coefficient of 0.9977 and limit of detection (LOD) of 1.03 x 10(-6) mol L(-1) (SIN = 3). The recoveries in tablet and syrup formulations were found as 97.4 and 90.8% with the relative standard deviations of 0.62 and 1.04%, respectively, which closely agree with those measured by high performance liquid chromatography (HPLC) with UV detector. Therefore, it was concluded that the PPy electrode can be used as an alternative novel potentiometric detector material for determination of sulfamethoxazole in pharmaceuticals with the advantages of easy preparation and regeneration capability of the electrode surface.